1. Field of the Invention
The invention relates to a magnetic spin valve sensor typically used in a magnetic disk drive; and, more specifically, to a magnetic spin valve sensor having an antiparallel tab structure with an exchange stabilization layer recessed from the active track edge.
2. Description of the Background Art
Disk drives using magnetic recording of digital information store most of the data in contemporary computer systems. A disk drive has at least one rotating disk with discrete concentric tracks of data. Each disk drive also has at least one recording head typically having a separate write element and read element for writing and reading the data on the tracks. The recording head is constructed on a slider and the slider is attached to a suspension. The combination of the recording head, slider, and suspension is called a head gimbal assembly. In addition, there is an actuator which positions the recording head over the specific track of interest. The actuator first rotates to seek the track of interest. After positioning the recording head over the track, the actuator maintains the recording head in close registration to that track. The disk in a disk drive has a substrate and a magnetic layer formed over the substrate for magnetic recording. The slider carrying the recording head has a disk facing surface upon which an air bearing is constructed. The air bearing allows the slider to float on a cushion of air and to be positioned close the disk surface. Alternatively, the slider surface facing the disk can be adapted for partial or continuous contact with the disk.
Magnetic spin valve sensors are used as the read element in most contemporary disk drives. A magnetic spin valve sensor is a sandwich of layers including a ferromagnetic pinned layer, a nonmagnetic electrically conducting layer, and a ferromagnetic free layer. The resistance of the spin valve sensor changes with respect to the direction and magnitude of an applied magnetic field such as the field from a written magnetic transition on a disk. To detect the change in resistance, sense current is passed through the sensor.
The free layer in a magnetic spin valve sensor is usually operated in the presence of a constant weak magnetic field to insure magnetic stability and prevent spurious signals. The application of a weak magnetic field to the sensor is sometimes referred to as magnetically biasing the sensor. One structure which may effectively be used for magnetic biasing is a pair of magnetic tabs which are antiparallel coupled to portions of the free layer. The antiparallel coupled tabs include a ferromagnetic biasing layer and an antiferromagnetic layer exchange coupled to the ferromagnetic biasing layer. This structure is effective; however, when the biasing layers are completely covered with the antiferromagnetic layer, the sensor becomes magnetically stiff and the sensitivity is degraded. Thus, with conventional sensors, sensitivity decreases as stability is achieved.
A magnetic spin valve sensor is needed which has antiparallel coupled biasing tabs and does not sacrifice sensitivity when attaining stability.